Process for fractionation of coke oven gas



Patented Sept. 1, 1931 PATENT OFFICE RICHARD LINDE, OF MUNICH, GERMANY.ASSIGNOR TO GESELLSCH AFT FUR LINDES EISMASCHINEN A. G., OFHOLLRIEGELSKREUTH, GERMANY, A CORPORATION OF EROCESS FOR FRACTIONATIONOF COKE OVEN GAS No Drawing. Application filed April 23, 1928, SerialNo. 272,355, and in Germany May 2, 1927.

In the fractionation of coke oven gas by partial liquefaction at lowtemperatures very troublesome disturbances have arisen in practicebecause of the separation of solid constituents and particularly becauseof the occurrence of explosions inside the separating apparatus. Againstthe supposition that the cause of these explosions is to be sought inthe acetylene content of the gases to be separated, is the observationthat solid acetylene, either alone 0.1 admixed with liquid hydrocarbons,cannot-be caused to explode by friction, sparking nor shocks in general.That the formation of copperacetylene is not the cause of the explosionsis indicated by the fact that this substance cannot be formed by thedirect action of acetylene even on finely divided copper.

In spite of these facts it hasbeen found that the troubles describedentirely disappear if, by suitable pretreatment according to the presentinvention, hydrocarbons con taining triple bonds are substantiallycompletely removed from the gases to be treated.

It is noteworthy that a quantitative removal of these hydrocarbons,which would be very difficult one large scale with the means heretoforeavailable, is not necessary,

3 but that it is sufiicient to so decrease their amount that on coolingthe gases there is no separation of acetylenes in the solid state.

This result is attained by reducing the content to about 1/100%, whichamount can be obtained without difficulty by the known methods ofremoving acetylene.

Experiments have lead to the conclusion that contrary to expectations,the presence of acetylene hydrocarbons is the cause of the explosions,and indeed it has been found, that, in the presence of auxiliary agentswhich attack copper, such as ammonia or nitric oxide, these hydrocarbonscan form explosive compounds with the copper of theseparating apparatus.This reaction takes place particularly at ordinary temperature orslightly lower. If an explosion takes place in the presence of solidacetylene the latter takes part in the explosion and greatly 5 increasesthe effect. Besides the heretofore against 'the efl'ect of acetylene.

known metallicor copper-acetylene compounds there are formedhigh-molecular compounds of high boiling pointpolymerization products ofdiacetylene, nitro compounds, etc.which can likewise take part in theexplosions, and which can cause a gradual encrustation of the separatingapparatus. For these reasons a separation of large amounts of solidacetylenes in the separating apparatus is to be avoided. On the otherhand a slight residue of acetylenes in the gases is unharmful as it isdissolved in the other hydrocarbons present on cooling the gases and iscontinually removed from the apparatus in solution. The term separatingapparatus is used herein to mean the-whole apparatus including theapparatus which the gas to be treated enters at a temperature ofapproximately 40 C., the heat exchangers and the fractionating apparatusproper.

To attain more certain security against the above mentioned disturbancestwo additional means may be utilized:

First the impurities present in the gases which favor the reaction ofacetylene hydrocarbons with copper, particularly ammonia, nitric oxideand water vapor, can be removed as far as possible with known absorptionmeans, such as concentrated sulfuric acid.

Further, all parts of the separating apparatus which consist of copperor copper alloys can be given a protective coating I have foundthat sucha coatin is effectively produced by a thin la er of tin, lead oralloysof these metals. hese metals would have seemed to be unsuitable,since they are readily attacked by the traces of sulfur compoundspresent in all gases. However, it has been found by experiment that inspite of this apparent disadvantage, the coatings of these metalscompletely resist the chemical and mechanical action to which they aresubjected in the se arating apparatus, while on the other ban thecertainty and ease with which completely covering coatings may beformed, is a particular advantage of the metals named.

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The removal of acetylene-hydrocarbons may be accomplished by passing thecompressed gases, after sulfur compounds and carbon dioxide have beenremoved in the usual manner and before entering the separatingapparatus, over heated catalysts, which causes a hydrogenation or adecomposition of acetylene. Other chemical processes may also be used,such as polymerization of the acetylenes with heated copper,precipitation of the acetylenes with metal salt solutions, oxidation ofthe acetylenes,

etc. Physical methods, for instance absorption in solvents, such aswater or acetone, may also be applied.

The process of the above mentioned German application 69,937 isessentially as follows:

The'gas mixture containing acetylene is passed before cooling atatmospheric or higher pressure over suitable catalysts heated up'to100400 0., for instance over partially dehydrated hydroxides ofaluminium The process may be carried out in an apparatus comprisingperiodically reversible regenerators for the inflowing and outflowinggases which are to be brought'into heat interchange with one another,means for supplying the necessary additional heat in this process, and areaction chamber filled with catalyst and arranged between the re--generators, all heated parts being insulated from heat interchange withthe surround ings.

I claim:

1. A preliminary treatment preparatory to the fractionation of coke ovengases .at low temperatures whichcomprises separating from said gashydrocarbons containing triple bonds, before any portion of the gasesare liquefied, to such an extent that the said hydrocarbons are notdeposited in solid form in the subsequent liquefaction andfractionation.

2. A )reliminary treatment preparatory to the raetionation of coke ovengases at low temperatures which comprises separating from said gashydrocarbons containing triple bonds, before any portion of the gasesare liquefied, to such an extent that the said hydrocarbons are notdeposited in solid form in the subsequent liquefaction and fractionationand also removing from said gases compounds 'which activate the actionof acetylene wi th copper.

3. A- preliminary treatment preparatory to the fractionation of cokeoven gases at low temperatures which comprises separating from said gashydrocarbons containing triple bonds, before any portion of the gasesare liquefied, to such an extent that the said hydrocarbons are notdeposited in solid form in the subsequent liquefaction and fractionationand also removing from said gases ammonia nitric oxide and water vapor.

In testimony whereof, I afiix my signature.

, Dn. RICHARD LINDE.

